By the time of Constantine, Christianity had spread widely throughout the eastern half of the Roman Empire. Asia Minor was then largely Christian. Thrace, Macedonia, Epirus, and Greece were all ecclesiastical provinces with their own metropolitans. Many Christians were found in Syria and Egypt. Churches also existed in Mesopotamia and Arabia, and even beyond the boundaries of the empire in Armenia and Persia. Between the time of Constantine and that of Justinian, Christianity continued to expand in the East, until the gospel had been carried to such distant regions as Abyssinia and India. UNION OF CHURCH AND STATE Most of the Christian communities in the Orient owed allegiance to the patriarchs of Constantinople, Jerusalem, Antioch, and Alexandria. The Roman emperor, however, was the supreme religious authority in the East. He felt it as much his duty to maintain the doctrines and organization of Christianity as to preserve the imperial dominions against foreign foes. Since he presided over the Church, there could be no real independence for its officers. Bishops, metropolitans, and patriarchs were in every respect subordinate to his will. This union of Church and State formed one of the most characteristic features of Christianity in the East. THEOLOGICAL DISPUTES; HERESIES Eastern Christians, far more than those in the West, devoted themselves to theological speculations. Constantinople and the great Hellenistic cities of Antioch and Alexandria contained many learned scholars who had prolonged and heated arguments over subtle questions of belief. After the Arian controversy had been settled in the fourth century, other disputes concerning the true nature of Christ broke out. These gave rise to many heresies. NESTORIANISM The heresy known as Nestorianism, from Nestorius, a patriarch of Constantinople, spread widely in the East. Nestorian missionaries even penetrated to India, China, and Mongolia. The churches which they established were numerous and influential during the Middle Ages, but since then most of them have been destroyed by the Mohammedans. Members of this sect are still to be found, however, in eastern lands. [11] [Illustration: THE NESTORIAN MONUMENT Evidence of Nestorian missions in China is afforded by the famous monument at Chang-an, province of Shensi. The stone, which was set up in 781 A.D., commemorates by an inscription in Chinese characters and the figure of a cross the introduction of Christianity into northwestern China. A replica of the Nestorian monument was taken to the United States in 1908 A.D. and was deposited in the Metropolitan Museum of Art, New York.] ORTHODOXY